The use of bottom-up approaches to semiconductor fabrication has grown in interest within the semiconductor industry. One such approach utilizes self-assembling block copolymers for generation of sublithographic ground rule nanometer scale patterns.
Self-assembling copolymer materials that are capable of self-organizing into nanometer-scale patterns may be applied within a recessed region of a template layer to form a nanoscale structure. Under suitable conditions, the two or more immiscible polymeric block components separate into two or more different phases on a nanometer scale, and thereby form ordered patterns of isolated nano-sized structural units. Such ordered patterns of isolated nano-sized structural units formed by the self-assembling block copolymers can be used for fabricating nano-scale structural units in semiconductor, optical, and magnetic devices. Dimensions of the structural units so formed are typically in the range of 5 to 40 nm, which are sublithographic (i.e., below the resolution of the lithographic tools).
The self-assembling block copolymers are first dissolved in a suitable solvent system to form a block copolymer solution, which is then applied onto the surface of an underlayer to form a block copolymer layer. The self-assembling block copolymers are annealed at an elevated temperature to form two sets of polymer block structures containing two different polymeric block components. The polymeric block structure may be lines or cylinders. One set of polymer block structures may be embedded in the other set of polymer block structures, or polymeric block structures belonging to different sets may alternate. The self-assembling block copolymers are non-photosensitive resists, of which the patterning is effected not by photons, i.e., optical radiation, but by self-assembly under suitable conditions such as an anneal.
While self-assembly of the two sets of polymer block structures by an anneal is an inherent chemical property of the self-assembling block copolymers, self-alignment of the two sets of polymer block structures requires an interaction of the self-assembling block copolymers with a physically constraining environment. In other words, the self-alignment of the two sets of polymer block structures requires an external structure to register the self-aligned structures to. Such an external structure functions as a template for registry of the self-aligned structure during the anneal that separates a first polymeric block component and a second polymeric block component.
The effective range of order generated by the external structure generates and effecting the self-alignment of the self-assembling block copolymers during anneal is finite. In other words, the spatial extent of the effect of the presence of the external structure as a template is limited, and does not propagate indefinitely. The coherence of the order is lost if the distance between the self-assembling block copolymers and the external structure exceeds the effective range. In this case, the two sets of polymer block structures no longer register with the external structure. While the size of a self-assembled self-aligned nanoscale structure may vary depending on the composition of the self-assembling block copolymers, the limited range, typically comprising less than 100 alterations of the first polymeric block component and the second polymeric block component. Thus, it is difficult to form a self-assembled self-aligned nanoscale structure having a dimension exceeding about 1 micron.
However, a large repetitive patterned structure is highly desirable for advanced semiconductor devices and nanoscale devices. Therefore, there is a need for a nanoscale self-assembled self-aligned structure that extends over a large area and having a size that is not limited by inherent effective range of the self-assembling block copolymers, and methods of forming such a nanoscale self-assembled self-aligned structure.